Process of treating low-grade ores and tailings by electrolysis.



No. 756,223. Y PATENTED APR; 5, 1904. E. PAHRIG. v PROGESS or TREATING LOW GRADE ORES AND T'AILINGS, BY ELECTROLYSISv APPLICATION IILED MAY 9, 1903.

I0 IODEL.

-; UNITED STATES Patented April 5, 1904.

PATENT OFFICE.

PROCESS OF TREATING LOW-GRADE ORES AND TAILINGS BY ELECTROLYSIS.

SPECIFICATION forming part of Letters Patent No. 756,223, dated April 5, 1904. Application filed May 9, 1903. Serial No. 156,392. (No specimens.)

To all whom/it TIMI/y concern:

Be it known that I, E Ns'r-FAHRIG, a citizen of the United States, residing in Philadelphia,-

in the county of Philadelphia and State'of Pennsylvania, have invented certain new. and

useful Improvements inProcesses of Treating Low-Grade Ores and Tailings by Electrolysis, of which the following is a specification. This invention relates to an improved process of treating low-grade ore and tailings containing a low percentage of precious metals, so that the same can be worked up effectively by electrolysis.

In many mines heretofore abandoned owing to the low percentage of gold and silver contained in the-ores it is possible to work up the same, also the accumulated tailings of aban-- doned mines, by my improved process, as the same is adapted to regain; almost every trace of precious metal contained in the ores and tailings in a successful manner and at a low expense, giving a yield of metal which com-.

pensates for the cost of installation and operation.

For this purpose the invention consistsof a process of treating low-grade ores and tailings by electrolysis by conducting amixture of the finely-ground ores or tailings, water,

and a suitable electrolyte forming a-pulp by gravity alternately into contact with inclined cathode and anode plates, collecting the ,de-. posited film of precious metals by scraping the same from said cathode-plates, subjecting the ores or tailings after this electrolytic extraction to an oxidizing and leaching action,

and finally subjecting them to an electrolytic 1 separation by precipitation, as willbe fully described hereinafter and finally pointed out in the claims.

The accompanying drawing'represents an apparatus for carrying out my improved process of treating low-grade ores and tailings by electrolysis, part in vertical section and part in side elevation.

In carrying out my improved process the ore and tailings are crushed.to any desired mesh above 20 and are then conducted to an elevator E;and duri1ped by the same into a charging-vat A. To the charging vat .A a

suitable electrolyte is added, and water is ad- I mitted by a supply-pipe at, having a valve (0, that passes through the bottom of the vat untilthe quantity of water and electrolyte admitted amounts to about sixty per cent. of the Weight of the dry ore or tailings, which produces a pulp sufliciently liquidto flow through the pipe C, which is connected with the circulatvat A and which serves to lift the pulp from the vat A through a stand-pipe C to the upper end of a tower T. The tower T is made of square or rectangular shape, according to the capacity required. The frame of the tower is suitably held together by stay pieces separated by about three feet from each other. 7 The toweris provided with two doors that extendthe full length of the same and are hinged to the side walls of the tower-frame. In the interior of the tower T are arranged, at equal distances from each other, metal grooves m for the reception of the cathode-plates D. The lower sufficient space to permit that amount of liquid pulp to pass readily over the cathodeplates and between the same and the opposite 'wall corresponding to the capacity of the pipe C.- The edge of the cathode-plates is on the doors, which are connected with one pole of the dynamo, form a reliable contact with the inclined cathode-plates. When opening the doors, the cathodes can be readily removed from the tower by slidingthem out of their grooved guideways for stripping or scraping off the deposit on the same. The cathodes D are made of sheet-copper or other suitable metal of sufficient thickness and strength for resisting the volume and pressure ofthe pulp passing over the. same for treatment. Below each cathode is arranged an inclined anode B, which is made of graphite or other suitable material and securely attached to the frames of the side walls orto thedoors the opposite poleof the dynamo.- A dynamo G of low voltage and ample amperage is suiting-pump P, that is located below the charging-- even with the edge of the frame, so that when the doors are closed suitable contact-springs of the tower.' The anodes are connected with ends (Z of the cathode-plates D are turned up so ode.

ably connected with a switchboard H, which is provided with a rheostat or regulator R, a voltmeter V, ammcter M, and a main switch S and complete the necessary electrolytic apparatus. The voltage is approximately five to seven volts, and the amperage corresponds to 0.08 to 0.1 ampere per square foot of cath- However, I do not wish to confine myself thereto, as it depends on the constituency and character of the ore under treatment. For the electrolytic precipitation of precious metals from solution I prefer two to five volts and from 0.05 to 0.06 ampere per square foot of cathode-plate.

In the charging-vat A is arranged a mercurytrap N, into which the pulp is discharged from the chute D below the lowermost cathode-plate D of the tower T until it overflows from and runs into the charging-vat A. The electrolyzing action is kept up in the tower for about one hour per ton of ore charged. The electrolyzing action is due to the oxidation of the quickened surface of the cathodeplates, as the nascent hydrogen constantly escaping from the pulp during the passage of the same through the tower has a tendency to quicken the cathode-plates, and thus keep the amalgam in a condition to easily retain any precious metal which might be in the pulp. Moreover, the electromotive force by virtue of the nascent hydrogen, chlorin, and oxygen, as the case may be, according to the character of the electrolyte used, decomposes the particles of metal in the mineral-containin g earthy matter and gangue, so that the precious-metal particles are brightened, and thus prepared to be either retained by amalgamation or to be brought by the continued action of the active electrolyte under a suitable electromotive force into solution.

The stand-pipe C is connected by a valved branch pipe G with an inclined rifiie-trough F, which is made of suitable length and provided at its bottom with transverse rifiies f equidistant from each other for catching any heavy or coarse material, iron pyrites, or concentrates, so that the clear pulp can pass over the rifilesf and into a leaching-tank L. This tank is gradually filled with the different charges obtained from the charging-vat A after the precious metal contained in the same has been partially extracted by the electrolytic action of the tower. When the tank L is filled, the pulp or ore, water, and electrolyte mixture feeding into the vat A is interrupted and the liquid flows through pipe It, provided with a valve 6, to the vatA, through the tower T, over the riflie-trough F, back to the leaching-tank L. This is continued until tests taken from time to time show that the precious metals have been sufiiciently extracted by the electric current.

It has been found by practical tests that from twelve to eighteen hours of electrolyzing and oxidizing is suflicient for leaving the pulp in the leaching-tank for about from ten to twelve hours, after which the liquid, still containing some metal, may be drawn off by decantation or other suitable means and either run through a filter -press or the precious metal still contained therein recovered by subjecting it again to electrolytic precipitation or any well-known method-as, for instance, to the action of a large battery-in which the traces of precious metal still contained in the leached mass may be extracted, While the remaining portion is run off as waste.

The riflle-trough F, over which the extracted pulp is passed, has the double object of agitating the pulp and thoroughly oxidizing it while passing over the rifiles f in the rifiletrough. A set of blow-pipes is connected with each vat and rifiie-trough for a still more thorough oxidizing of the pulp.

The electrolyte employed may be any oxy chlorid or chlorids, or a weak solution of potassium cyanid or hypochlorid, or any other electrolyte may be used.

My improved process of treating low-grade ores or tailings is carried on as follows: The ore is mixed in the charging-vat A with a suitable quantity of water and a suitable electrolyte, as any oxychlorid or chlorid, or a weak solution of potassium cyanid or hypochlorid, which mixture forms a pulp which is pumped up through the stand -pipe to the hopper-shaped upper end T of the electrolytic tower T, in which it traverses alternately between a pair of cathode-plates D and anodeplates B and is thus subjected to the electrolytic action of the current. The precious metals are deposited on the cathode-plates D, which are removed from time to time from the tower and scraped or stripped. The cathodes and anodes are so arranged in their relative positions that the pulp under a pressure corresponding to a section of the side of the tower is forced to make contact between the under surfaceof the anode and the upper surface of the cathode plates. The partiallyextracted pulp passes from the lower end of the tower T into the mercury trap N and overflows in the charging-vat A, from which it is lifted again by the stand-pipe C, this treatment being kept up for about an hour per ton of ore charged. After the greater quantity of precious metals in the pulp are deposited by the electrolytic action the twoway valve G is turned and the partially-extracted pulp of the vat A caused to pass over the riffies f of the rifiie-trough F into the leaching-tank L. The process of charging the tank A, subjecting the pulp to electrolytic action, and discharging the charge of partiallyextracted pulp onto and over the rifiie-trough F and into the leaching-tank L is repeated until the capacity of the leaching-tank is reached. The pulp which has been subjected to this process is permitted to stand in the leaching-tank for some time, whereupon it is riflie-trough F, until the tests show that the metals contained therein are sufiiciently extracted by the electrolytic action of the current. Finally, the partially-extracted pulp is subjected to filtration or decantation to regain from the filtered or decanted liquor the precious metal in solution. The liquor is heated to 120 or 130 Fahrenheit and then subjected, preferably by steam, to electrolysis in an electrical depositing or precipitation battery,

or both, also charged from the dynamo. The

pulp, after a second washing for the lasttrace of precious metal in solution, is run off as waste.

The tower action and the automatic action from beginning to end enables a large-amount of work to be done with the least possible manual labor, while the tower action, in which the repeated rise and fall of pulp takes place through a space filled with an oxidizing atmosphere at a pressure equal to the height of the tower, has an extraordinary effect on the ore under treatment.

The use of my improved process will cause the reworking of mines which are now abandoned, as the amount of precious metals obtained thereby compensates for the cost of installation and operation in a short time.

Having thus described my invention, I claim as new and desire to secure by Letters Patent 1. The process herein described of treating low-grade ores and tailings by electrolysis for regaining the precious metals contained in the same, which consists in grinding the ore or tailings, then mixing the same with a suitable quantity of-water and a suitable electrolyte so as to form apulp, passing said pulp by gravity between a series of pairs of inclined anode and cathode plates arranged tower fashion one below the other, and removing from time to time the precious metal deposited on said cathodeplates, substantially as set forth.

2. The process herein described of treating low-grade ores and tailings by electrolysis, which consists in subjecting a pulp of ore or tailings, water and a suitable electrolyte toan electrolytic action by passing the same by gravity between alternately-inclined pairs of anode and cathode plates arranged in a tower one below the other so as to deposit the precious metals on the cathode-plates, subjecting the partially-extracted pulp to an oxidizing action, and then to a leaching action, and finally to a second electrolytic action for removing the remaining traces of precious metal, substantially as set forth. 7

3. The process herein described of treating low-grade ores and tailings by electrolysis,

which consists in subjecting a pulp of ore or tailings, water and a suitable electrolyte to an electrolytic action by passing the same between a plurality of pairs of inclined anode and cathode plates arranged in a tower one below the other for depositing the precious metals thereon, subjecting the partially-extracted pulp to an oxidizing action, then to a leaching action for some time, and then to a successive electrolytic, oxidizing and leaching action, until the precious metals in the partially-extracted pulp have been almost completely dissociated, dissolved and gone into solution, and finally to the electrolytic action of a battery for obtaining the remaining traces of the precious metal, substantially as set forth.

4. The process herein described of treating low-grade ores and tailings by electrolysis, which consists in subjecting a pulp of ore or tailings, water and a suitable electrolyte to an electrolytic action by passing the same between a plurality of pairs of alternately-inclined anode and cathode plates arrangedin a tower one below the other-for depositing the precious metals thereon, subjecting the partially-extracted pulp to an oxidizing action, then to a leaching action for some time, then to a successive electrolytic, oxidizing and leaching action, until the precious metals have been almost completely dissociated, dissolved and gone into solution, then subjecting the same to defecation, heating the defecated liquor, and finally subjecting the liquor to an electrolytic action, substantially as set forth.

5. The process herein described of treating low-grade ores and tailings by electrolysis, which consists in repeatedly passing a mixture of ground ore or tailings, water and a suitable electrolyte between a series of pairs of alternately inclined anode and cathode plates arranged tower fashion one below. the other, substantially as set forth.

6. The process herein described of treating low-grade -ores and tailings by electrolysis,

which consists in passing a mixture of ground ore or tailings, water and a'suitable electrolyte between a series of pairs of alternatelyinclined anode and cathode plates arranged tower fashion one below the other in an oxidizing atmosphere at apressure equal to the height of the tower, substantially as set forth.

In testimony that I claim the foregoing as my invention I have signed my name in presence of two subscrlbmg witnesses.

, ERNST FAHRIG.

Witnesses:

PAUL GoEPEL, C. P. GoEPEL. 

